全文获取类型
收费全文 | 1542篇 |
免费 | 41篇 |
出版年
2024年 | 5篇 |
2023年 | 16篇 |
2022年 | 36篇 |
2021年 | 74篇 |
2020年 | 25篇 |
2019年 | 53篇 |
2018年 | 48篇 |
2017年 | 41篇 |
2016年 | 48篇 |
2015年 | 82篇 |
2014年 | 78篇 |
2013年 | 115篇 |
2012年 | 107篇 |
2011年 | 92篇 |
2010年 | 51篇 |
2009年 | 55篇 |
2008年 | 71篇 |
2007年 | 54篇 |
2006年 | 82篇 |
2005年 | 62篇 |
2004年 | 54篇 |
2003年 | 42篇 |
2002年 | 33篇 |
2001年 | 15篇 |
2000年 | 17篇 |
1999年 | 14篇 |
1998年 | 7篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 10篇 |
1994年 | 14篇 |
1993年 | 11篇 |
1992年 | 7篇 |
1991年 | 12篇 |
1989年 | 4篇 |
1988年 | 9篇 |
1987年 | 7篇 |
1986年 | 11篇 |
1985年 | 17篇 |
1984年 | 6篇 |
1983年 | 9篇 |
1982年 | 6篇 |
1981年 | 9篇 |
1980年 | 11篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1973年 | 6篇 |
排序方式: 共有1583条查询结果,搜索用时 15 毫秒
81.
Iqbal Farheena Krzeminska-Ahmadzai Urszula Ayub Qasim Wilson Robyn Song Beng Kah Fahim Muhammad Rahman Sadequr 《Biological invasions》2022,24(3):861-878
Biological Invasions - What kind of genetic structure helps the rapid range expansion of the invasive species is fundamental to understand spread of invasion. The House crow (Corvus splendens), an... 相似文献
82.
Shaheen A. Afridi W. A. Mahboob S. Sana M. Zeeshan N. Ismat F. Mirza O. Iqbal M. Rahman M. 《Molecular Biology》2019,53(4):596-605
Molecular Biology - Acriflavine resistance protein B (AcrB) serves as prototype for multidrug resistance (MDR) efflux transporters of resistance nodulation division (RND) superfamily. AcrB has been... 相似文献
83.
Iqbal Aneela Khan Raham Sher Shehryar Kashmala Imran Anum Ali Faryal Attia Syeda Shah Shahen Mii Masahiro 《Plant Cell, Tissue and Organ Culture》2019,137(1):1-10
Plant Cell, Tissue and Organ Culture (PCTOC) - Four serotypes of the dengue virus that can cause severe disease in humans greatly increases the complexity of vaccine development. In this study, we... 相似文献
84.
85.
Mahmood Hossain Siddique Mohammad Raqibul Hasan Rubaiot Abdullah S. M. Costello Liam Matieu Henry Iqbal Md. Zaheer Akhter Mariam 《Wetlands Ecology and Management》2019,27(4):553-569
Wetlands Ecology and Management - Bangladesh has the single largest tract of naturally growing mangrove forest as well as the world’s largest manmade mangrove forest on newly accreted land in... 相似文献
86.
Rashmin khanam Raj kumar Iram Iqbal Hejazi Syed Shahabuddin Ramovatar Meena Paulraj Rajamani Nitin Yadav Asif Iqbal Bhat Fareeda Athar 《Journal of cellular biochemistry》2019,120(2):1651-1666
N-benzhydrylpiperazine and 1,3,4-oxadiazoles are pharmacologically active scaffolds which exhibits significant inhibitory growth effects against various cancer cells, however, antiproliferation effects and the underlying mechanism for inducing apoptosis for aforementioned scaffolds addressing HeLa cancer cells remains uncertain. In this study, N-benzhydrylpiperazine clubbed with 1,3,4-oxadiazoles ( 4a–4h ) were synthesized, subsequently characterized using high resolution spectroscopic techniques and eventually evaluated for their antiproliferation potential by inducing apoptosis in HeLa cancer cells. The MTT assay screening results revealed that among all, compound 4d ( N-benzhydryl-4-((5-(4-aminophenyl)-1,3,4-oxadiazol-2-yl)methyl)piperazine) in particular, exhibited IC 50 value of 28.13 ± 0.21 μg/mL and significantly inhibited the proliferation of HeLa cancer cells in concentration-dependent manner. The in vitro anticancer assays for treated HeLa cells resulted in alterations in the cell morphology, reduction in colony formation, and inhibition of cell migration in concentration-dependent treatment. Furthermore, G2/M phase arrest, variations in the nuclear morphology, degradation of chromosomal DNA confirmed the ongoing apoptosis in treated HeLa cells. Increase in the expression of cytochrome C and caspase-3 confirmed the involvement of intrinsic mitochondrial pathway regulating the cell death. Also, elevation in reactive oxygen species level and loss of mitochondrial membrane potential signified that compound 4d induced apoptosis in HeLa cells by generating the oxidative stress. Therefore, compound 4d may act as a potent chemotherapeutic agent against human cervical cancer. 相似文献
87.
Analysis of the relative amount and distribution pattern of phloem sclerenchyma in some 29 tropical trees of India was carried out with systematic considerations. Both the features exhibited considerable diversity among the species analyzed. The extent of area occupied by sclerenchyma in transections of the bark of these species varied from zero to 35% and 3 to 49% in the conducting and non-conducting phloem zones respectively, the overall amount constituting about 3 to 45% of the secondary phloem as a whole. The sclerenchyma cells differentiated either as isolated elements or in the form of bands or fascicles of diverse shape and size showing various distribution patterns. 相似文献
88.
This study, aimed at elucidating changes in the foliar and cambial behavior in Azadirachta indica (Neem tree) due to coal-smoke pollution, has revealed inhibitory effects of pollution stress on leaf pigments concentrations, nitrate reductase activity and the contents of reducing sugars and total N content, whereas stimulatory effects were given on stomatal index and nitrate and sulphur contents. Under smoke effects, stomatal conductance was low, leading to a drop in the net photosynthetic rate and a rise in the internal CO2 concentration of leaf. Cambial reactivation in the stem was delayed at the polluted site. Although the total span of the cambial activity was reduced, greater amount of wood was observed to accumulate in the stem axis under heavy pollution stress. Vessel proportion in the wood increased, whereas size of vessel elements and xylem fibers decreased. “Vulnerability factor” (ratio between mean vessel diameter and mean vessel abundance) and “mesomorphic ratio” (multiplication product of vulnerability factor and mean length of vessel element) of the stem–wood, both declined with increase in the pollution stress, thus indicating a tendency of the species for shifting towards xeromorphy when grown under stress. Given the opposite trends of photosynthetic rate and wood increment, the carbon-partitioning pattern rather than the photosynthetic rate seems to have influenced the accumulation of new wood. The Neem tree proves to be suitable for growing in the polluted areas. 相似文献
89.
In a previous study [Wang et al. (1996) Nat. Med. 2, 871-875], Wang et al. found (i) that abnormally hyperphosphorylated tau (AD P-tau) isolated from Alzheimer's disease (AD) brain as paired helical filaments (PHF)-tau and as cytosolic AD P-tau but not tau from normal brain were stained by lectins, and (ii) that on in vitro deglycosylation the PHF untwisted into sheets of thin straight filaments, suggesting that tau only in AD brains is glycosylated. To elucidate the primary structure of N-glycans, we comparatively analyzed the N-glycan structures obtained from PHF-tau and AD P-tau. More than half of N-glycans found in PHF-tau and AD P-tau were different. High mannose-type sugar chains and truncated N-glycans were found in both taus in addition to a small amount of sialylated bi- and triantennary sugar chains. More truncated glycans were richer in PHF-tau than AD P-tau. This enrichment of more truncated glycans in PHF might be involved in promoting the assembly and or stabilizing the pathological fibrils in AD. 相似文献
90.
Coudron TA Iqbal M Rice WC Ellersieck MR Pinnell RE 《Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology》1999,124(3):231-240
The compatibility of the venom from the parasitic species Euplectrus comstockii Howard (Hymenoptera: Eulophidae) with the pathogenicity of Autographa californica (Speyer) (Lepidoptera: Noctuidae) MNPV baculovirus (AcMNPV) was tested in third and fourth instar larvae of Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae). The presence of AcMNPV did not alter the ability of the venom to arrest ecdysis in T. ni larvae. The presence of the venom delayed the rate of viruses by AcMNPV but increased the total mortality rates from days 9 to 14 in both third and fourth instar T. ni larvae. The delay in viruses was minimized by administering the virus prior to envenomation. In the presence of the venom, the final LD50 values were lower for fourth instar larvae than for third instar larvae. Surface response equations were developed to visualize the effect of the venom on the viruses caused by AcMNPV. 相似文献